The present invention relates to a TFT array substrate of a thin film transistor liquid crystal display (TFT LCD) and a manufacturing method thereof.
In order to effectively reduce the manufacturing cost of a TFT LCD and improve its yield, the manufacturing process of the newly developed active driven TFT array substrate has been gradually simplified, for example, from a seven- or a six-photolithography process at the beginning to a current widely employed five-photolithography process. Recently, a four-photolithography process based on a slit photolithography process (a gray tone photolithography process) is applied in the field of TFT LCD manufacturing, the core step of which is to replace the second photolithography (an active layer photolithography) and the third photolithography (a source/drain metal layer photolithography) of the conventional five-photolithography process with one slit photolithography process. The detailed procedure of the four-photolithography process is described as follows.
Firstly, a gate metal layer is deposited on a substrate, a gate line and a gate electrode are formed by the first photolithography, and then a gate insulating layer, an active layer, an ohmic contact layer, and a source/drain metal layer are sequentially deposited on the gate line and the gate electrode on the substrate.
Next, with a slit photolithography process, a data line, an active area, source/drain electrodes, and a TFT channel pattern are formed through a source/drain metal layer wet etching and a multi-step etching (active layer etching-ashing-dry etching-ohmic contact layer etching).
Then, a passivation layer is deposited on the substrate and a via hole is formed in the passivation layer by the third photolithography.
Finally, a transparent conductive layer is deposited on the substrate and a pixel electrode is formed by the fourth photolithography and the pixel electrode is connected with one of the source/drain electrodes.
Compared with the conventional five-photolithography process, the four-photolithography process is mainly characterized in that the patterns of the active layer and the source/drain metal layer are formed by a single slit photolithography process, resulting in reduction of the production cycle and the manufacturing cost. However, since the process employs a slit mask, which requires a strict manufacturing accuracy for the photolithography, difficulty and cost for developing the process are increased remarkably and it is hard to increase the yield.